Protesters wanting to deliver a message to world leaders in London for this week's G-20 summit gathered outside the high walls of the Bank of England in the heart of London's financial quarter on Wednesday and demonstrated over everything from the meltdown in the financial system to the growing threat from climate change. Some people got a little too excited; after protesters broke windows at the nearby headquarters of the Royal Bank of Scotland  which recently needed a government bailout to avoid going under  one or two people looted the lender's computer equipment. A few dozen more scuffled with police outside, but overall the protest was less violent than many had feared.

The financial storms may have only gathered recently, but noisy, tempestuous crowds like this one have been banding together on London's street for years  securing the freedom of prisoners in the 17th century, protesting the lack of rights for women in the early 1900s and railing against an unpopular tax just under two decades ago. As always, the mood today was mercurial. Organizers of the gathering, a movement calling itself G-20 Meltdown, had promised a "peaceful and fun street party." For much of the protest, that's what they got. While anarchists, many dressed from head to toe in black, threw paint at the bank and beer cans and insults at police, most kept their protests peaceful. By late afternoon, with police still skirmishing with some, two dozen demonstrators had been arrested and a handful of officers injured. (See pictures of the protests in London.)

In warm sunshine  so often the backdrop to bloody protests in London, from the anti-Catholic Gordon riots of the 18th century to the Notting Hill race riots in the 1950s  marchers set off for the bank from four of the capital's underground stations, each group led by a "horseman of the apocalypse." At London Bridge, protesters walked to the blast of a trombone with a medley of motives. "Can we overthrow the government?" bellowed Chris Knight, one of the event's organizers. "Yes we can!" Beside an effigy of Fred Goodwin, the former boss of the Royal Bank of Scotland, who is blamed for its collapse, Knight predicted that "bankers should be hanging from lampposts" later in the day. (See pictures of the global financial crisis.)

Others had different aims in mind. Duncan Blinkhorn, a 47-year-old charity worker pulling a solar-powered sound system on the back of his bicycle, came to warn G-20 leaders that "climate change [is] approaching a possible tipping point." Seventeen-year-old Max Warwick, decked out in Doc Marten boots and drainpipe jeans and holding an English flag emblazoned with "Gordon Is a Moron," just wanted his government "to do stuff for working-class families," he said, puffing on a neatly rolled cigarette. With tongue in cheek, Delores Forothers  think about it  was marching "to support all these bankers," she said in her best fake-posh accent. "Greed," she added, a black feather boa around her neck, "is good." (See pictures of Michelle Obama's fashion sense.)

Spotting a banker for her to get behind wasn't easy. Employers had suggested that financial workers dress down for the day, fearful a baying mob could set about them. That was never likely. While some outside the Bank of England jeered at the staff standing behind its leaded windows, others waved. Those workers who did brave the streets went unmolested. Riccardo Dilorenzo, an immaculately suited property developer stepping out from a nearby office, even dared to label the protesters "hypocrites" since "half of them don't work." (Even he, though, might have admired the opportunism of others; street hawkers' "antigovernment whistles"  strangely similar to standard ones  could be bought for a pound.)

On Bishopsgate, one of the financial quarter's busiest streets, a separate climate-change protest opted for fun over fracas. Campaigners set up tents, strung bunting and danced to salsa music. Emerging from his purple and green domed tent, 19-year-old student Charlie Game said "something big, visual and positive" was the best way to get politicians to face up to the issue. But while he hoped that he and his friends would be allowed to camp out for a while, he "didn't want to cause much trouble." But trouble is what protesting is often about in London. And today's demonstrations may not be the last this year.